If you select the FormsProtectionEnum.All value, the system uses the configured data-validation algorithm, based on the machineKey tag. This is the default, and recommended, value.
If you select FormsProtectionEnum.None, cookies might be subject to plaintext attacks.
If you select FormsProtectionEnum.Validation, the cookie is created using cookie validation by concatenating a validation key with the cookie data, computing a Message Authentication Code (MAC), and appending the MAC to the outgoing cookie.